getImageReader(ImageWriter writer)
Returns an ImageReadercorresponding to the given
ImageWriter, if there is one, or null
if the plug-in for this ImageWriter does not
specify a corresponding ImageReader, or if the
given ImageWriter is not registered.

getImageTranscoders(ImageReader reader,
ImageWriter writer)
Returns an Iterator containing all currently
registered ImageTranscoders that claim to be
able to transcode between the metadata of the given
ImageReader and ImageWriter.

getImageWriter(ImageReader reader)
Returns an ImageWritercorresponding to the given
ImageReader, if there is one, or null
if the plug-in for this ImageReader does not
specify a corresponding ImageWriter, or if the
given ImageReader is not registered.

getImageWriters(ImageTypeSpecifier type,
String formatName)
Returns an Iterator containing all currently
registered ImageWriters that claim to be able to
encode images of the given layout (specified using an
ImageTypeSpecifier) in the given format.

scanForPlugins

Scans for plug-ins on the application class path,
loads their service provider classes, and registers a service
provider instance for each one found with the
IIORegistry.

This method is needed because the application class path can
theoretically change, or additional plug-ins may become available.
Rather than re-scanning the classpath on every invocation of the
API, the class path is scanned automatically only on the first
invocation. Clients can call this method to prompt a re-scan.
Thus this method need only be invoked by sophisticated applications
which dynamically make new plug-ins available at runtime.

The getResources method of the context
ClassLoader is used locate JAR files containing
files named
META-INF/services/javax.imageio.spi.classname,
where classname is one of ImageReaderSpi,
ImageWriterSpi, ImageTranscoderSpi,
ImageInputStreamSpi, or
ImageOutputStreamSpi, along the application class
path.

The contents of the located files indicate the names of
actual implementation classes which implement the
aforementioned service provider interfaces; the default class
loader is then used to load each of these classes and to
instantiate an instance of each class, which is then placed
into the registry for later retrieval.

The exact set of locations searched depends on the
implementation of the Java runtime enviroment.

setUseCache

public static void setUseCache(boolean useCache)

Sets a flag indicating whether a disk-based cache file should
be used when creating ImageInputStreams and
ImageOutputStreams.

When reading from a standard InputStream>, it
may be necessary to save previously read information in a cache
since the underlying stream does not allow data to be re-read.
Similarly, when writing to a standard
OutputStream, a cache may be used to allow a
previously written value to be changed before flushing it to
the final destination.

The cache may reside in main memory or on disk. Setting
this flag to false disallows the use of disk for
future streams, which may be advantageous when working with
small images, as the overhead of creating and destroying files
is removed.

On startup, the value is set to true.

Parameters:

useCache - a boolean indicating whether a
cache file should be used, in cases where it is optional.

setCacheDirectory

Sets the directory where cache files are to be created. A
value of null indicates that the system-dependent
default temporary-file directory is to be used. If
getUseCache returns false, this value is ignored.

createImageInputStream

Returns an ImageInputStream that will take its
input from the given Object. The set of
ImageInputStreamSpis registered with the
IIORegistry class is queried and the first one
that is able to take input from the supplied object is used to
create the returned ImageInputStream. If no
suitable ImageInputStreamSpi exists,
null is returned.

The current cache settings from getUseCacheand
getCacheDirectory will be used to control caching.

Parameters:

input - an Object to be used as an input
source, such as a File, readable
RandomAccessFile, or InputStream.

createImageOutputStream

Returns an ImageOutputStream that will send its
output to the given Object. The set of
ImageOutputStreamSpis registered with the
IIORegistry class is queried and the first one
that is able to send output from the supplied object is used to
create the returned ImageOutputStream. If no
suitable ImageOutputStreamSpi exists,
null is returned.

The current cache settings from getUseCacheand
getCacheDirectory will be used to control caching.

Parameters:

output - an Object to be used as an output
destination, such as a File, writable
RandomAccessFile, or OutputStream.

getImageWriter

Returns an ImageWritercorresponding to the given
ImageReader, if there is one, or null
if the plug-in for this ImageReader does not
specify a corresponding ImageWriter, or if the
given ImageReader is not registered. This
mechanism may be used to obtain an ImageWriter
that will understand the internal structure of non-pixel
metadata (as encoded by IIOMetadata objects)
generated by the ImageReader. By obtaining this
data from the ImageReader and passing it on to the
ImageWriter obtained with this method, a client
program can read an image, modify it in some way, and write it
back out preserving all metadata, without having to understand
anything about the structure of the metadata, or even about
the image format. Note that this method returns the
"preferred" writer, which is the first in the list returned by
javax.imageio.spi.ImageReaderSpi.getImageWriterSpiNames().

getImageReader

Returns an ImageReadercorresponding to the given
ImageWriter, if there is one, or null
if the plug-in for this ImageWriter does not
specify a corresponding ImageReader, or if the
given ImageWriter is not registered. This method
is provided principally for symmetry with
getImageWriter(ImageReader). Note that this
method returns the "preferred" reader, which is the first in
the list returned by
javax.imageio.spi.ImageWriterSpi.getImageReaderSpiNames().

read

Returns a BufferedImage as the result of decoding
a supplied File with an ImageReader
chosen automatically from among those currently registered.
The File is wrapped in an
ImageInputStream. If no registered
ImageReader claims to be able to read the
resulting stream, null is returned.

The current cache settings from getUseCacheand
getCacheDirectory will be used to control caching in the
ImageInputStream that is created.

Note that there is no read method that takes a
filename as a String; use this method instead after
creating a File from the filename.

This methods does not attempt to locate
ImageReaders that can read directly from a
File; that may be accomplished using
IIORegistry and ImageReaderSpi.

Parameters:

input - a File to read from.

Returns:

a BufferedImage containing the decoded
contents of the input, or null.

read

Returns a BufferedImage as the result of decoding
a supplied InputStream with an ImageReader
chosen automatically from among those currently registered.
The InputStream is wrapped in an
ImageInputStream. If no registered
ImageReader claims to be able to read the
resulting stream, null is returned.

The current cache settings from getUseCacheand
getCacheDirectory will be used to control caching in the
ImageInputStream that is created.

This methods does not attempt to locate
ImageReaders that can read directly from an
InputStream; that may be accomplished using
IIORegistry and ImageReaderSpi.

Parameters:

input - an InputStream to read from.

Returns:

a BufferedImage containing the decoded
contents of the input, or null.

read

Returns a BufferedImage as the result of decoding
a supplied URL with an ImageReader
chosen automatically from among those currently registered. An
InputStream is obtained from the URL,
which is wrapped in an ImageInputStream. If no
registered ImageReader claims to be able to read
the resulting stream, null is returned.

The current cache settings from getUseCacheand
getCacheDirectory will be used to control caching in the
ImageInputStream that is created.

This methods does not attempt to locate
ImageReaders that can read directly from a
URL; that may be accomplished using
IIORegistry and ImageReaderSpi.

Parameters:

input - a URL to read from.

Returns:

a BufferedImage containing the decoded
contents of the input, or null.

read

Returns a BufferedImage as the result of decoding
a supplied ImageInputStream with an
ImageReader chosen automatically from among those
currently registered. If no registered
ImageReader claims to be able to read the stream,
null is returned.

Parameters:

stream - an ImageInputStream to read from.

Returns:

a BufferedImage containing the decoded
contents of the input, or null.

write

Writes an image using the an arbitrary ImageWriter
that supports the given format to an
ImageOutputStream. The image is written to the
ImageOutputStream starting at the current stream
pointer, overwriting existing stream data from that point
forward, if present.